BRAIN AGING: MOLECULAR EFFECTS OF PERINATAL NUTRITION

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The overall goal of Project 0001 is to determine the molecular mechanisms involved in brain reorganization governed by prenatal availability of choline. Aim 1 is to test the hypothesis that prenatal choline availability modulates developmental patterns of gene expression by altering DNA methylation of the regulatory elements of genes whose expression is controlled by 5-methylcytosine content, based on the evidence showing that choline, via its action as a donor of methyl groups, can alter DNA methylation profiles and gene expression in vivo. We will study DNA methylation of selected genes known to be regulated by DNA methylation and whose expression in brain is modulated by prenatal availability of choline (e.g. insulin-like growth factor II, lgf2). Aim 2 is to test the hypothesis that prenatal choline availability alters the development and aging of selected neuronal populations that can be identified by gene expression profiles. Using oligonucleotide microarrays, we found that the expression pattern of multiple hippocampal and cerebral cortical genes, including receptor ligands, receptors, protein kinases, and transcription factors (e.g. Igf2, GABABR1, TrkB, Camkl, Camkllbeta, PKCbeta2, and Zif268), is modulated by the prenatal availability of choline. We will map the expression of these proteins using immunoblotting, in situ hybridization, and immunohistochemistry (with the Neuroanatomy Core) in order to identify the relevant neuronal populations. Aim 3 is to test the hypothesis that individual requirements for choline depend on genotype. Several genes encoding proteins involved in the metabolism of choline and of methyl groups display potymorphism in humans and cause metabolic abnormalities that, in some cases, can be successfully treated with nutritional strategies. Genetic mouse models of these conditions will be used to obtain information on the mechanisms by which alterations in the supply of choline can modulate the phenotype of these animals. Four models will be studied, including mice with targeted mutations in apolipoprotein E (Apoe), phosphatidylethanoamine N-methyltransferease, methylenetetrahydrofolate reductase, and choline dehydrogenase. Project 3 has shown that cognitive defects observed in Apoe null mice can be rescued by choline supplementation throughout gestation, thus providing the experimental paradigm for these studies. In the four mouse models, we will determine gene expression patterns and signal transduction mechanisms, sensitive to prenatal choline availability, including MAPK and CREB phosphorylation and acetylcholine turnover, and the effects of dietary choline on their phenotypes.